DISPOSITIONS AND ACQUISITIONS (Assets Held for Sale - Freeport Cobalt) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2018	Dec. 21, 2018
Assets
Cash and cash equivalents	$ 2,020	$ 3,657
Trade accounts receivable	741	892
Property, plant, equipment and mine development costs, net	29,584	29,818
Other assets	1,885	1,560
Total previously included in current assets held for sale	40,809	42,144	$ 42,216
Liabilities
Accounts payable and accrued liabilities	2,576	2,708
Accrued income taxes	119	324
Deferred income taxes and asset retirement obligations	4,206	4,408
Total previously included in current liabilities held for sale	23,361	$ 23,476
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member] | Freeport Cobalt
Long Lived Assets Held-for-sale [Line Items]
Disposal Group, Including Discontinued Operation, Cash	59
Disposal Group, Including Discontinued Operation, Assets	271
Liabilities
Disposal Group, Including Discontinued Operation, Liabilities	63
Disposal Group, Including Discontinued Operation, Consideration	200
Disposal Group, Including Discontinued Operation, Consideration, Working Capital	$ 50
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member] | Lundin Mining Corporation [Member] | Freeport Cobalt
Long Lived Assets Held-for-sale [Line Items]
Disposal Group, Including Discontinued Operation, Proceeds On Sale, Percent	30.00%
PT Freeport Indonesia [Member]
Long Lived Assets Held-for-sale [Line Items]
Ownership percentage		48.76%		81.28%